1. Field of the Invention
The present invention relates to a temperature detection circuit, and more particularly to a temperature detection circuit for detecting a temperature of a semiconductor integrated device and a method of adjusting the same.
2. Background Art
Electronic devices including semiconductor integrated devices are configured to activate a protection circuit when the device temperature inside exceeds a predetermined temperature in order to prevent a malfunction or damage occurring from heat generation during operation. For example, a thermistor may be used to detect the temperature inside a device. Thermistors typically have large manufacturing variations. For accurate temperature detection, expensive thermistors with less manufacturing variations have needed to be used.
To detect the temperature inside an electronic device without using a temperature sensor such as a thermistor, a technique for generating a temperature-independent reference voltage by a bandgap reference circuit has been proposed (for example, see FIG. 1 of Patent Literature 1). The bandgap reference circuit generates a negative feedback voltage for equalizing the base-emitter voltages of first transistors (65 to 67) and second transistors (68 to 70) having different emitter areas by an operational amplifier (61), and outputs the voltage as a reference voltage (Vbgr). The base-emitter voltages decrease with the increasing semiconductor temperature. Since the first transistors and the second transistors have different emitter areas as described above, the degree of decrease of the base-emitter voltages of the first transistors due to a temperature increase is different from that of the base-emitter voltages of the second transistors due to the temperature increase. At absolute zero, the base-emitter voltages converge to the band gab voltage resulting from the semiconductor band gap energy irrespective of the emitter areas. In other words, the difference between the base-emitter voltages of the respective first and second transistors corresponds to the amount of voltage change due to the temperature change. The foregoing operational amplifier then operates to cancel the amounts of decrease of the base-emitter voltages due to the temperature change, whereby a reference voltage having the band gap voltage independent of temperature changes is generated.
However, the resistors (R1 to R5), the transistors (65 to 70), and the operational amplifier (61) used in the bandgap reference circuit are also subject to characteristic changes because of manufacturing variations. There has thus been the problem that accurate temperature detection is difficult.